/*

 * jdphuff.c

 *

 * Copyright (C) 1995, Thomas G. Lane.

 * This file is part of the Independent JPEG Group's software.

 * For conditions of distribution and use, see the accompanying README file.

 *

 * This file contains Huffman entropy decoding routines for progressive JPEG.

 *

 * Much of the complexity here has to do with supporting input suspension.

 * If the data source module demands suspension, we want to be able to back

 * up to the start of the current MCU.  To do this, we copy state variables

 * into local working storage, and update them back to the permanent

 * storage only upon successful completion of an MCU.

 */



#define JPEG_INTERNALS

#include "jinclude.h"

#include "jpeglib.h"

#include "jdhuff.h"		/* Declarations shared with jdhuff.c */





#ifdef D_PROGRESSIVE_SUPPORTED



/*

 * Expanded entropy decoder object for progressive Huffman decoding.

 *

 * The savable_state subrecord contains fields that change within an MCU,

 * but must not be updated permanently until we complete the MCU.

 */



typedef struct {

  unsigned int EOBRUN;			/* remaining EOBs in EOBRUN */

  int last_dc_val[MAX_COMPS_IN_SCAN];	/* last DC coef for each component */

} savable_state;



/* This macro is to work around compilers with missing or broken

 * structure assignment.  You'll need to fix this code if you have

 * such a compiler and you change MAX_COMPS_IN_SCAN.

 */



#ifndef NO_STRUCT_ASSIGN

#define ASSIGN_STATE(dest,src)  ((dest) = (src))

#else

#if MAX_COMPS_IN_SCAN == 4

#define ASSIGN_STATE(dest,src)  \

	((dest).EOBRUN = (src).EOBRUN, \

	 (dest).last_dc_val[0] = (src).last_dc_val[0], \

	 (dest).last_dc_val[1] = (src).last_dc_val[1], \

	 (dest).last_dc_val[2] = (src).last_dc_val[2], \

	 (dest).last_dc_val[3] = (src).last_dc_val[3])

#endif

#endif





typedef struct {

  struct jpeg_entropy_decoder pub; /* public fields */



  /* These fields are loaded into local variables at start of each MCU.

   * In case of suspension, we exit WITHOUT updating them.

   */

  bitread_perm_state bitstate;	/* Bit buffer at start of MCU */

  savable_state saved;		/* Other state at start of MCU */



  /* These fields are NOT loaded into local working state. */

  unsigned int restarts_to_go;	/* MCUs left in this restart interval */



  /* Pointers to derived tables (these workspaces have image lifespan) */

  d_derived_tbl * derived_tbls[NUM_HUFF_TBLS];



  d_derived_tbl * ac_derived_tbl; /* active table during an AC scan */

} phuff_entropy_decoder;



typedef phuff_entropy_decoder * phuff_entropy_ptr;



/* Forward declarations */

METHODDEF boolean decode_mcu_DC_first JPP((j_decompress_ptr cinfo,

					   JBLOCKROW *MCU_data));

METHODDEF boolean decode_mcu_AC_first JPP((j_decompress_ptr cinfo,

					   JBLOCKROW *MCU_data));

METHODDEF boolean decode_mcu_DC_refine JPP((j_decompress_ptr cinfo,

					    JBLOCKROW *MCU_data));

METHODDEF boolean decode_mcu_AC_refine JPP((j_decompress_ptr cinfo,

					    JBLOCKROW *MCU_data));





/*

 * Initialize for a Huffman-compressed scan.

 */



METHODDEF void

start_pass_phuff_decoder (j_decompress_ptr cinfo)

{

  phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;

  boolean is_DC_band, bad;

  int ci, coefi, tbl;

  int *coef_bit_ptr;

  jpeg_component_info * compptr;



  is_DC_band = (cinfo->Ss == 0);



  /* Validate scan parameters */

  bad = FALSE;

  if (is_DC_band) {

    if (cinfo->Se != 0)

      bad = TRUE;

  } else {

    /* need not check Ss/Se < 0 since they came from unsigned bytes */

    if (cinfo->Ss > cinfo->Se || cinfo->Se >= DCTSIZE2)

      bad = TRUE;

    /* AC scans may have only one component */

    if (cinfo->comps_in_scan != 1)

      bad = TRUE;

  }

  if (cinfo->Ah != 0) {

    /* Successive approximation refinement scan: must have Al = Ah-1. */

    if (cinfo->Al != cinfo->Ah-1)

      bad = TRUE;

  }

  if (cinfo->Al > 13)		/* need not check for < 0 */

    bad = TRUE;

  if (bad)

    ERREXIT4(cinfo, JERR_BAD_PROGRESSION,

	     cinfo->Ss, cinfo->Se, cinfo->Ah, cinfo->Al);

  /* Update progression status, and verify that scan order is legal.

   * Note that inter-scan inconsistencies are treated as warnings

   * not fatal errors ... not clear if this is right way to behave.

   */

  for (ci = 0; ci < cinfo->comps_in_scan; ci++) {

    int cindex = cinfo->cur_comp_info[ci]->component_index;

    coef_bit_ptr = & cinfo->coef_bits[cindex][0];

    if (!is_DC_band && coef_bit_ptr[0] < 0) /* AC without prior DC scan */

      WARNMS2(cinfo, JWRN_BOGUS_PROGRESSION, cindex, 0);

    for (coefi = cinfo->Ss; coefi <= cinfo->Se; coefi++) {

      int expected = (coef_bit_ptr[coefi] < 0) ? 0 : coef_bit_ptr[coefi];

      if (cinfo->Ah != expected)

	WARNMS2(cinfo, JWRN_BOGUS_PROGRESSION, cindex, coefi);

      coef_bit_ptr[coefi] = cinfo->Al;

    }

  }



  /* Select MCU decoding routine */

  if (cinfo->Ah == 0) {

    if (is_DC_band)

      entropy->pub.decode_mcu = decode_mcu_DC_first;

    else

      entropy->pub.decode_mcu = decode_mcu_AC_first;

  } else {

    if (is_DC_band)

      entropy->pub.decode_mcu = decode_mcu_DC_refine;

    else

      entropy->pub.decode_mcu = decode_mcu_AC_refine;

  }



  for (ci = 0; ci < cinfo->comps_in_scan; ci++) {

    compptr = cinfo->cur_comp_info[ci];

    /* Make sure requested tables are present, and compute derived tables.

     * We may build same derived table more than once, but it's not expensive.

     */

    if (is_DC_band) {

      if (cinfo->Ah == 0) {	/* DC refinement needs no table */

	tbl = compptr->dc_tbl_no;

	if (tbl < 0 || tbl >= NUM_HUFF_TBLS ||

	    cinfo->dc_huff_tbl_ptrs[tbl] == NULL)

	  ERREXIT1(cinfo, JERR_NO_HUFF_TABLE, tbl);

	jpeg_make_d_derived_tbl(cinfo, cinfo->dc_huff_tbl_ptrs[tbl],

				& entropy->derived_tbls[tbl]);

      }

    } else {

      tbl = compptr->ac_tbl_no;

      if (tbl < 0 || tbl >= NUM_HUFF_TBLS ||

          cinfo->ac_huff_tbl_ptrs[tbl] == NULL)

        ERREXIT1(cinfo, JERR_NO_HUFF_TABLE, tbl);

      jpeg_make_d_derived_tbl(cinfo, cinfo->ac_huff_tbl_ptrs[tbl],

			      & entropy->derived_tbls[tbl]);

      /* remember the single active table */

      entropy->ac_derived_tbl = entropy->derived_tbls[tbl];

    }

    /* Initialize DC predictions to 0 */

    entropy->saved.last_dc_val[ci] = 0;

  }



  /* Initialize bitread state variables */

  entropy->bitstate.bits_left = 0;

  entropy->bitstate.get_buffer = 0; /* unnecessary, but keeps Purify quiet */

  entropy->bitstate.printed_eod = FALSE;



  /* Initialize private state variables */

  entropy->saved.EOBRUN = 0;



  /* Initialize restart counter */

  entropy->restarts_to_go = cinfo->restart_interval;

}





/*

 * Figure F.12: extend sign bit.

 * On some machines, a shift and add will be faster than a table lookup.

 */



#ifdef AVOID_TABLES



#define HUFF_EXTEND(x,s)  ((x) < (1<<((s)-1)) ? (x) + (((-1)<<(s)) + 1) : (x))



#else



#define HUFF_EXTEND(x,s)  ((x) < extend_test[s] ? (x) + extend_offset[s] : (x))



static const int extend_test[16] =   /* entry n is 2**(n-1) */

  { 0, 0x0001, 0x0002, 0x0004, 0x0008, 0x0010, 0x0020, 0x0040, 0x0080,

    0x0100, 0x0200, 0x0400, 0x0800, 0x1000, 0x2000, 0x4000 };



static const int extend_offset[16] = /* entry n is (-1 << n) + 1 */

  { 0, ((-1)<<1) + 1, ((-1)<<2) + 1, ((-1)<<3) + 1, ((-1)<<4) + 1,

    ((-1)<<5) + 1, ((-1)<<6) + 1, ((-1)<<7) + 1, ((-1)<<8) + 1,

    ((-1)<<9) + 1, ((-1)<<10) + 1, ((-1)<<11) + 1, ((-1)<<12) + 1,

    ((-1)<<13) + 1, ((-1)<<14) + 1, ((-1)<<15) + 1 };



#endif /* AVOID_TABLES */





/*

 * Check for a restart marker & resynchronize decoder.

 * Returns FALSE if must suspend.

 */



LOCAL boolean

process_restart (j_decompress_ptr cinfo)

{

  phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;

  int ci;



  /* Throw away any unused bits remaining in bit buffer; */

  /* include any full bytes in next_marker's count of discarded bytes */

  cinfo->marker->discarded_bytes += entropy->bitstate.bits_left / 8;

  entropy->bitstate.bits_left = 0;



  /* Advance past the RSTn marker */

  if (! (*cinfo->marker->read_restart_marker) (cinfo))

    return FALSE;



  /* Re-initialize DC predictions to 0 */

  for (ci = 0; ci < cinfo->comps_in_scan; ci++)

    entropy->saved.last_dc_val[ci] = 0;

  /* Re-init EOB run count, too */

  entropy->saved.EOBRUN = 0;



  /* Reset restart counter */

  entropy->restarts_to_go = cinfo->restart_interval;



  /* Next segment can get another out-of-data warning */

  entropy->bitstate.printed_eod = FALSE;



  return TRUE;

}





/*

 * Huffman MCU decoding.

 * Each of these routines decodes and returns one MCU's worth of

 * Huffman-compressed coefficients. 

 * The coefficients are reordered from zigzag order into natural array order,

 * but are not dequantized.

 *

 * The i'th block of the MCU is stored into the block pointed to by

 * MCU_data[i].  WE ASSUME THIS AREA IS INITIALLY ZEROED BY THE CALLER.

 *

 * We return FALSE if data source requested suspension.  In that case no

 * changes have been made to permanent state.  (Exception: some output

 * coefficients may already have been assigned.  This is harmless for

 * spectral selection, since we'll just re-assign them on the next call.

 * Successive approximation AC refinement has to be more careful, however.)

 */



/*

 * MCU decoding for DC initial scan (either spectral selection,

 * or first pass of successive approximation).

 */



METHODDEF boolean

decode_mcu_DC_first (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)

{   

  phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;

  int Al = cinfo->Al;

  register int s, r;

  int blkn, ci;

  JBLOCKROW block;

  BITREAD_STATE_VARS;

  savable_state state;

  d_derived_tbl * tbl;

  jpeg_component_info * compptr;



  /* Process restart marker if needed; may have to suspend */

  if (cinfo->restart_interval) {

    if (entropy->restarts_to_go == 0)

      if (! process_restart(cinfo))

	return FALSE;

  }



  /* Load up working state */

  BITREAD_LOAD_STATE(cinfo,entropy->bitstate);

  ASSIGN_STATE(state, entropy->saved);



  /* Outer loop handles each block in the MCU */



  for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {

    block = MCU_data[blkn];

    ci = cinfo->MCU_membership[blkn];

    compptr = cinfo->cur_comp_info[ci];

    tbl = entropy->derived_tbls[compptr->dc_tbl_no];



    /* Decode a single block's worth of coefficients */



    /* Section F.2.2.1: decode the DC coefficient difference */

    HUFF_DECODE(s, br_state, tbl, return FALSE, label1);

    if (s) {

      CHECK_BIT_BUFFER(br_state, s, return FALSE);

      r = GET_BITS(s);

      s = HUFF_EXTEND(r, s);

    }



    /* Convert DC difference to actual value, update last_dc_val */

    s += state.last_dc_val[ci];

    state.last_dc_val[ci] = s;

    /* Scale and output the DC coefficient (assumes jpeg_natural_order[0]=0) */

    (*block)[0] = (JCOEF) (s << Al);

  }



  /* Completed MCU, so update state */

  BITREAD_SAVE_STATE(cinfo,entropy->bitstate);

  ASSIGN_STATE(entropy->saved, state);



  /* Account for restart interval (no-op if not using restarts) */

  entropy->restarts_to_go--;



  return TRUE;

}





/*

 * MCU decoding for AC initial scan (either spectral selection,

 * or first pass of successive approximation).

 */



METHODDEF boolean

decode_mcu_AC_first (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)

{   

  phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;

  int Se = cinfo->Se;

  int Al = cinfo->Al;

  register int s, k, r;

  unsigned int EOBRUN;

  JBLOCKROW block;

  BITREAD_STATE_VARS;

  d_derived_tbl * tbl;



  /* Process restart marker if needed; may have to suspend */

  if (cinfo->restart_interval) {

    if (entropy->restarts_to_go == 0)

      if (! process_restart(cinfo))

	return FALSE;

  }



  /* Load up working state.

   * We can avoid loading/saving bitread state if in an EOB run.

   */

  EOBRUN = entropy->saved.EOBRUN; /* only part of saved state we care about */



  /* There is always only one block per MCU */



  if (EOBRUN > 0)		/* if it's a band of zeroes... */

    EOBRUN--;			/* ...process it now (we do nothing) */

  else {

    BITREAD_LOAD_STATE(cinfo,entropy->bitstate);

    block = MCU_data[0];

    tbl = entropy->ac_derived_tbl;



    for (k = cinfo->Ss; k <= Se; k++) {

      HUFF_DECODE(s, br_state, tbl, return FALSE, label2);

      r = s >> 4;

      s &= 15;

      if (s) {

        k += r;

        CHECK_BIT_BUFFER(br_state, s, return FALSE);

        r = GET_BITS(s);

        s = HUFF_EXTEND(r, s);

	/* Scale and output coefficient in natural (dezigzagged) order */

        (*block)[jpeg_natural_order[k]] = (JCOEF) (s << Al);

      } else {

        if (r == 15) {		/* ZRL */

          k += 15;		/* skip 15 zeroes in band */

        } else {		/* EOBr, run length is 2^r + appended bits */

          EOBRUN = 1 << r;

          if (r) {		/* EOBr, r > 0 */

	    CHECK_BIT_BUFFER(br_state, r, return FALSE);

            r = GET_BITS(r);

            EOBRUN += r;

          }

	  EOBRUN--;		/* this band is processed at this moment */

	  break;		/* force end-of-band */

	}

      }

    }



    BITREAD_SAVE_STATE(cinfo,entropy->bitstate);

  }



  /* Completed MCU, so update state */

  entropy->saved.EOBRUN = EOBRUN; /* only part of saved state we care about */



  /* Account for restart interval (no-op if not using restarts) */

  entropy->restarts_to_go--;



  return TRUE;

}





/*

 * MCU decoding for DC successive approximation refinement scan.

 * Note: we assume such scans can be multi-component, although the spec

 * is not very clear on the point.

 */



METHODDEF boolean

decode_mcu_DC_refine (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)

{   

  phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;

  int p1 = 1 << cinfo->Al;	/* 1 in the bit position being coded */

  int blkn;

  JBLOCKROW block;

  BITREAD_STATE_VARS;



  /* Process restart marker if needed; may have to suspend */

  if (cinfo->restart_interval) {

    if (entropy->restarts_to_go == 0)

      if (! process_restart(cinfo))

	return FALSE;

  }



  /* Load up working state */

  BITREAD_LOAD_STATE(cinfo,entropy->bitstate);



  /* Outer loop handles each block in the MCU */



  for (blkn = 0; blkn < cinfo->blocks_in_MCU; blkn++) {

    block = MCU_data[blkn];



    /* Encoded data is simply the next bit of the two's-complement DC value */

    CHECK_BIT_BUFFER(br_state, 1, return FALSE);

    if (GET_BITS(1))

      (*block)[0] |= p1;

    /* Note: since we use |=, repeating the assignment later is safe */

  }



  /* Completed MCU, so update state */

  BITREAD_SAVE_STATE(cinfo,entropy->bitstate);



  /* Account for restart interval (no-op if not using restarts) */

  entropy->restarts_to_go--;



  return TRUE;

}





/*

 * MCU decoding for AC successive approximation refinement scan.

 */



METHODDEF boolean

decode_mcu_AC_refine (j_decompress_ptr cinfo, JBLOCKROW *MCU_data)

{   

  phuff_entropy_ptr entropy = (phuff_entropy_ptr) cinfo->entropy;

  int Se = cinfo->Se;

  int p1 = 1 << cinfo->Al;	/* 1 in the bit position being coded */

  int m1 = (-1) << cinfo->Al;	/* -1 in the bit position being coded */

  register int s, k, r;

  unsigned int EOBRUN;

  JBLOCKROW block;

  JCOEFPTR thiscoef;

  BITREAD_STATE_VARS;

  d_derived_tbl * tbl;

  int num_newnz;

  int newnz_pos[DCTSIZE2];



  /* Process restart marker if needed; may have to suspend */

  if (cinfo->restart_interval) {

    if (entropy->restarts_to_go == 0)

      if (! process_restart(cinfo))

	return FALSE;

  }



  /* Load up working state */

  BITREAD_LOAD_STATE(cinfo,entropy->bitstate);

  EOBRUN = entropy->saved.EOBRUN; /* only part of saved state we care about */



  /* There is always only one block per MCU */

  block = MCU_data[0];

  tbl = entropy->ac_derived_tbl;



  /* If we are forced to suspend, we must undo the assignments to any newly

   * nonzero coefficients in the block, because otherwise we'd get confused

   * next time about which coefficients were already nonzero.

   * But we need not undo addition of bits to already-nonzero coefficients;

   * instead, we can test the current bit position to see if we already did it.

   */

  num_newnz = 0;



  /* initialize coefficient loop counter to start of band */

  k = cinfo->Ss;



  if (EOBRUN == 0) {

    for (; k <= Se; k++) {

      HUFF_DECODE(s, br_state, tbl, goto undoit, label3);

      r = s >> 4;

      s &= 15;

      if (s) {

	if (s != 1)		/* size of new coef should always be 1 */

	  WARNMS(cinfo, JWRN_HUFF_BAD_CODE);

        CHECK_BIT_BUFFER(br_state, 1, goto undoit);

        if (GET_BITS(1))

	  s = p1;		/* newly nonzero coef is positive */

	else

	  s = m1;		/* newly nonzero coef is negative */

      } else {

	if (r != 15) {

	  EOBRUN = 1 << r;	/* EOBr, run length is 2^r + appended bits */

	  if (r) {

	    CHECK_BIT_BUFFER(br_state, r, goto undoit);

	    r = GET_BITS(r);

	    EOBRUN += r;

	  }

	  break;		/* rest of block is handled by EOB logic */

	}

	/* note s = 0 for processing ZRL */

      }

      /* Advance over already-nonzero coefs and r still-zero coefs,

       * appending correction bits to the nonzeroes.  A correction bit is 1

       * if the absolute value of the coefficient must be increased.

       */

      do {

	thiscoef = *block + jpeg_natural_order[k];

	if (*thiscoef != 0) {

	  CHECK_BIT_BUFFER(br_state, 1, goto undoit);

	  if (GET_BITS(1)) {

	    if ((*thiscoef & p1) == 0) { /* do nothing if already changed it */

	      if (*thiscoef >= 0)

		*thiscoef += p1;

	      else

		*thiscoef += m1;

	    }

	  }

	} else {

	  if (--r < 0)

	    break;		/* reached target zero coefficient */

	}

	k++;

      } while (k <= Se);

      if (s) {

	int pos = jpeg_natural_order[k];

	/* Output newly nonzero coefficient */

	(*block)[pos] = (JCOEF) s;

	/* Remember its position in case we have to suspend */

	newnz_pos[num_newnz++] = pos;

      }

    }

  }



  if (EOBRUN > 0) {

    /* Scan any remaining coefficient positions after the end-of-band

     * (the last newly nonzero coefficient, if any).  Append a correction

     * bit to each already-nonzero coefficient.  A correction bit is 1

     * if the absolute value of the coefficient must be increased.

     */

    for (; k <= Se; k++) {

      thiscoef = *block + jpeg_natural_order[k];

      if (*thiscoef != 0) {

	CHECK_BIT_BUFFER(br_state, 1, goto undoit);

	if (GET_BITS(1)) {

	  if ((*thiscoef & p1) == 0) { /* do nothing if already changed it */

	    if (*thiscoef >= 0)

	      *thiscoef += p1;

	    else

	      *thiscoef += m1;

	  }

	}

      }

    }

    /* Count one block completed in EOB run */

    EOBRUN--;

  }



  /* Completed MCU, so update state */

  BITREAD_SAVE_STATE(cinfo,entropy->bitstate);

  entropy->saved.EOBRUN = EOBRUN; /* only part of saved state we care about */



  /* Account for restart interval (no-op if not using restarts) */

  entropy->restarts_to_go--;



  return TRUE;



undoit:

  /* Re-zero any output coefficients that we made newly nonzero */

  while (num_newnz > 0)

    (*block)[newnz_pos[--num_newnz]] = 0;



  return FALSE;

}





/*

 * Module initialization routine for progressive Huffman entropy decoding.

 */



GLOBAL void

jinit_phuff_decoder (j_decompress_ptr cinfo)

{

  phuff_entropy_ptr entropy;

  int *coef_bit_ptr;

  int ci, i;



  entropy = (phuff_entropy_ptr)

    (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,

				SIZEOF(phuff_entropy_decoder));

  cinfo->entropy = (struct jpeg_entropy_decoder *) entropy;

  entropy->pub.start_pass = start_pass_phuff_decoder;



  /* Mark derived tables unallocated */

  for (i = 0; i < NUM_HUFF_TBLS; i++) {

    entropy->derived_tbls[i] = NULL;

  }



  /* Create progression status table */

  cinfo->coef_bits = (int (*)[DCTSIZE2])

    (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,

				cinfo->num_components*DCTSIZE2*SIZEOF(int));

  coef_bit_ptr = & cinfo->coef_bits[0][0];

  for (ci = 0; ci < cinfo->num_components; ci++) 

    for (i = 0; i < DCTSIZE2; i++)

      *coef_bit_ptr++ = -1;

}



#endif /* D_PROGRESSIVE_SUPPORTED */

